import React, { useEffect, useMemo, useRef, useState } from 'react'
import styled, { CSSProperties } from 'styled-components'
import { Icon } from '../icon'

const source = [
  {
    value: '北京分行',
    children: [
      {
        value: '朝阳支行办事处',
        children: [{ value: '朝阳支行办事处-1' }, { value: '朝阳支行办事处-2' }]
      },
      { value: '海淀支行办事处' },
      { value: '石景山支行办事处' }
    ]
  },
  {
    value: '天津分行',
    children: [
      { value: '和平支行办事处' },
      { value: '河东支行办事处' },
      { value: '南开支行办事处' }
    ]
  }
]

const root = {
  level: 0,
  visible: true,
  expand: true,
  children: source,
  value: 'root'
}

interface itemProps {
  value: string
  level?: number
  expand?: boolean
  visible?: boolean
  parent?: itemProps
  children?: Array<itemProps>
  key?: string
}

interface itemPropsRequired
  extends Omit<Required<itemProps>, 'children' | 'parent'> {
  children?: itemPropsRequired[]
  parent: itemPropsRequired
}
const checkParent = function (g: itemPropsRequired) {
  return g.level === 1
}

const levelSpace = 20 //同级生效间距
///1插上级 2插同级 3插下级 0不插
const switchInsert = function (diff: number, g: itemPropsRequired) {
  if (!isNaN(diff)) {
    const origin = g.level * 10 //目标原本padding
    if (diff < origin) {
      //移动到padding前全部算上级
      if (checkParent(g)) {
        //排除最顶级
        return 2
      } else {
        return 1
      }
    } else if (diff < origin + levelSpace) {
      return 2
    } else {
      return 3
    }
  } else {
    return 0
  }
}

const findOrigin = function (key: string, data: itemPropsRequired[]) {
  const res = data.filter(v => v.key === key)
  if (res.length > 0) {
    return res[0]
  } else {
    return null
  }
}
const getParent = function (g: itemPropsRequired) {
  if (g.parent && g.parent.parent) {
    return g.parent.parent
  } else {
    return g.parent
  }
}

const judgeChildren = function (
  origin: itemPropsRequired,
  target: itemPropsRequired
) {
  let sign = true //如果有孩子就是false
  const fn = (child: itemPropsRequired) => {
    if (child.children) {
      child.children.forEach(v => {
        if (v === target) {
          sign = false
          return
        }
        fn(v)
      })
    }
  }
  fn(origin)
  return sign
}
const changeOriginParent = function (origin: itemPropsRequired) {
  const parent = origin.parent
  if (parent.children) {
    const index = parent.children.indexOf(origin)
    if (index > -1) {
      parent.children.splice(index, 1)
    }
    //下面这个方法会产生bug
    //parent.children = parent.children.filter((v) => v !== origin);
  }
}

const changeTargetParent = function (
  parent: itemPropsRequired,
  origin: itemPropsRequired,
  g: itemPropsRequired
) {
  origin.parent = parent
  if (parent.children) {
    //判断应该插入父级节点哪里
    if (g.parent.children) {
      const index = g.parent.children.indexOf(g)
      if (index > -1) {
        parent.children.splice(index + 1, 0, origin)
      } else {
        //parent传递g会进来
        parent.children.push(origin)
      }
    } else {
      parent.children.push(origin)
    }
  } else {
    parent.children = [origin]
  }
}

const checkTargetOrigin = function (
  g: itemPropsRequired,
  origin: itemPropsRequired
) {
  return g !== origin
}

const insertTop = function (
  key: string,
  g: itemPropsRequired,
  data: itemPropsRequired[],
  callback: Function
) {
  const origin = findOrigin(key, data)
  //origin插入target上级
  const parent = getParent(g)
  if (
    g.level !== 1 &&
    origin &&
    checkTargetOrigin(g, origin) &&
    judgeChildren(origin, g)
  ) {
    //修改以前父节点
    changeOriginParent(origin)
    //修改目标父节点的父节点（与父节点同级）
    changeTargetParent(parent, origin, g)
    callback()
  }
}
const insertMiddle = function (
  key: string,
  g: itemPropsRequired,
  data: itemPropsRequired[],
  callback: Function
) {
  const origin = findOrigin(key, data)
  //origin插入target同级
  const parent = g.parent
  if (
    g.level !== 0 &&
    origin &&
    checkTargetOrigin(g, origin) &&
    judgeChildren(origin, g)
  ) {
    changeOriginParent(origin)
    changeTargetParent(parent, origin, g)
    callback()
  }
}

const insertLower = function (
  key: string,
  g: itemPropsRequired,
  data: itemPropsRequired[],
  callback: Function
) {
  const origin = findOrigin(key, data)
  const parent = g
  if (origin && checkTargetOrigin(g, origin) && judgeChildren(origin, g)) {
    changeOriginParent(origin)
    changeTargetParent(parent, origin, g)
    callback()
  }
}

const flatten = function (
  list: Array<itemProps>,
  level = 1,
  parent: itemProps,
  defaultExpand = true // 是否展开
): itemPropsRequired[] {
  let arr: itemPropsRequired[] = [] //收集所有子项
  list.forEach(item => {
    item.level = level
    if (item.expand === undefined) {
      item.expand = defaultExpand
    }
    if (item.visible === undefined) {
      item.visible = true
    }
    if (!parent.visible || !parent.expand) {
      item.visible = false
    }
    if (item.key === undefined) {
      item.key = item.value + Math.random()
    }

    item.parent = parent
    arr.push(item as itemPropsRequired)
    if (item['children']) {
      arr.push(...flatten(item['children'], level + 1, item, defaultExpand))
    }
  })
  return arr
}

const changeVisible = (item: itemPropsRequired, callback: Function) => {
  //给点击的children设置visible
  if (item.children) {
    //避免children有显示不一行为
    let visible: boolean
    const depth = (item: itemPropsRequired[]) => {
      item.forEach(v => {
        if (visible === undefined) {
          visible = !v.visible
        }
        v.visible = visible
        if (v.children) {
          //把孩子全部改掉
          depth(v.children)
        }
      })
    }
    depth(item.children)
    callback() //改完后更新页面
  }
}

/**
 * tree样式
 */

interface DragHighlight {
  drag: boolean
  itemkey: string
}

interface TreeItemType {
  level: number
  itemkey: string
  highlight: DragHighlight
}

const originPadding = 24 //原始间距

const TreeItem = styled.div<TreeItemType>`
  padding-left: ${props => originPadding * props.level}px;
  padding-top: 2px;
  padding-bottom: 2px;
  display: flex;
  align-items: center;
  position: relative;
  overflow: hidden;
  ${props => {
    if (props.highlight.drag && props.highlight.itemkey === props.itemkey) {
      return 'border: 1px dashed #53c94fa8;'
    } else {
      return ''
    }
  }}
`

const TreeIcon = styled.span<{ g: itemPropsRequired }>`
  & > svg {
    transition: linear 0.2s;
    height: 10px;
    margin-bottom: 5px;
    ${props => {
      if (props.g.children && props.g.children.length !== 0) {
        if (props.g.children[0] && props.g.children[0]['visible']) {
          return 'display:inline-block;transform: rotate(-90deg);'
        } else {
          return 'display:inline-block;'
        }
      } else {
        return 'opacity:0'
      }
    }};
  }
`
/**
 * 拖动标识
 */
interface DragControlData {
  drag: boolean
  x: number
  itemkey: string
}
type TreeGragType = { gkey: string } & DragControlData

const TreeGrag = styled.div<TreeGragType>`
  position: absolute;
  width: 100%;
  height: 90%;
  ${props => {
    switch (props.x) {
      case 1:
        return `margin-left:${-levelSpace}px ;`
      case 2:
        return ''
      case 3:
        return `margin-left:${levelSpace}px  ;`
      default:
        return ''
    }
  }};
  ${props => {
    if (props.itemkey === props.gkey) {
      return 'background: #00000030;'
    }
  }}
`

// 节流
export function throttle(fn: Function, delay: number = 300) {
  let flag = true
  return function (...args: any) {
    if (flag) {
      flag = false
      fn(...args)
      setTimeout(() => {
        flag = true
      }, delay)
    }
  }
}

// 拖动时显示的图片
const img = new Image()
img.src = 'https://www.easyicon.net/api/resizeApi.php?id=1200841&size=32'

export function Tree(props: TreeProps) {
  const root = useMemo(() => {
    return {
      level: 0,
      visible: true,
      expand: true,
      children: source,
      value: 'root'
    }
  }, [source])
  const [dragUpdate, setDragUpdate] = useState(0)
  const data = useMemo(() => {
    return flatten(root.children, 1, root)
    // eslint-disable-next-line react-hooks/exhaustive-deps
  }, [root, dragUpdate])
  const [start, setStart] = useState(0)
  const forceUpdate = useState(0)[1]
  const ref = useRef<HTMLDivElement>(null)
  useEffect(() => {
    if (ref.current) {
      setStart(ref.current.getBoundingClientRect().left) //为了找到起始
    }
  }, [])

  // 高亮拖拽元素
  const [highlight, setHighlight] = useState({
    drag: true,
    itemkey: ''
  })

  // 鼠标拖拽出去时
  useEffect(() => {
    const handler = () => {
      setDragOver(prev => ({ ...prev, drag: false }))
      setHighlight({
        drag: false,
        itemkey: ''
      })
    }
    window.addEventListener('dragend', handler)
    return () => {
      window.removeEventListener('dragend', handler)
    }
  }, [])

  const callback = () => {
    forceUpdate(state => state + 1)
  }
  const dragCallback = () => {
    setDragUpdate(state => state + 1)
  }

  const [dragOver, setDragOver] = useState<DragControlData>({
    drag: false,
    x: 0,
    itemkey: ''
  })

  const dragHandler = (
    clientX: number,
    itemkey: string,
    g: itemPropsRequired
  ) => {
    const diff = clientX - start
    const x = switchInsert(diff, g)
    setDragOver({
      drag: true,
      x,
      itemkey
    })
  }

  return (
    <div ref={ref}>
      {data
        .filter(v => v.visible === true)
        .map(g => {
          return (
            <TreeItem
              itemkey={g.key}
              highlight={highlight}
              level={g.level}
              draggable
              onClick={() => changeVisible(g, callback)}
              key={g.key}
              onDragStart={e => {
                e.dataTransfer.setData('atomkey', `${g.key}`)
                e.dataTransfer.setDragImage(img, 29, 29)
              }}
              onDragOver={e => {
                e.preventDefault()
                throttle(dragHandler)(e.clientX, g.key, g)
              }}
              onDrop={e => {
                const key = e.dataTransfer.getData('atomkey')
                const left = e.clientX
                const diff = left - start //离顶部差值
                const res = switchInsert(diff, g)
                switch (res) {
                  case 1:
                    insertTop(key, g, data, dragCallback)
                    break
                  case 2:
                    insertMiddle(key, g, data, dragCallback)
                    break
                  case 3:
                    insertLower(key, g, data, dragCallback)
                    break
                  default:
                    break
                }
              }}
            >
              <TreeIcon g={g}>
                <Icon icon="arrowdown"></Icon>
              </TreeIcon>
              <span>{g.value}</span>
              {dragOver.drag && (
                <TreeGrag
                  gkey={g.key}
                  drag={dragOver.drag}
                  x={dragOver.x}
                  itemkey={dragOver.itemkey}
                ></TreeGrag>
              )}
            </TreeItem>
          )
        })}
    </div>
  )
}

export type TreeProps = {
  /** 数据源*/
  source: itemProps[]
  /** 是否可以拖拽 */
  drag?: boolean
  /** 高亮边框颜色 */
  borderColor?: string
  /** 拖拽提示色 */
  backColor?: string
  /**外层样式*/
  style?: CSSProperties
  /**外层类名*/
  classname?: string
}
Tree.defaultProps = {
  source: [],
  drag: true,
  borderColor: '#53c94fa8',
  backColor: '#00000030'
}
